The invention of the present application concerns a magnetic sludge suitable for use in wastewater treatment, a method for preparing the same and a method for wastewater treatment by using the same.
Further, the invention of the present application concerns a novel method for wastewater treatment using inclusive fixed carrier which enables wastewater treatment at high efficiency by a facility at a reduced cost and which is also excellent in preventing clogging or channeling in a treatment tank, as well as an apparatus therefor.
As one of wastewater treatment techniques, an upflow/downflow anaerobic fixed bed reactor has been known.
However, this technique involves a drawback that suspended matters or grown microorganisms in wastewater clog the fixed bed to bring about pressure loss in passing water or bring about a channeling phenomenon in passing wastewater. Further, when a microorganism carrier is used for the fixed bed, the carrier floats on the water surface by buoyancy of gases generated from the carrier itself to give undesired effects on the treatment efficiency and the design of the apparatus. On the other hand, an upflow sludge blanket reactor has been considered to be an apparatus capable of solving the foregoing problems. However, this apparatus actually necessitates a gas-sludge separation device and involves a problem of complexity in view of the apparatus design such that a correct design is indispensable for a homogeneous dispersion inflow system at the bottom of a reactor. Further, it has a serious problem of requiring long set up period for the treatment operation such that it takes 3 to 4 months for forming granule sludges formed in the apparatus. Furthermore, formation of granule sludges utilizes deposition and agglomeration effect of microorganisms, and it has been reported that it does not function well in wastewater containing proteins or lipids.
In order to overcome such problems, while it has been considered effective to prepare sludges containing great amount of microorganisms in a short period of time and utilize them as biological membranes, as well as to control the movement of the biological membranes, such technical means has not yet been provided actually so far.
Further, an apparatus for wastewater treatment incorporating a fixed carrier for supporting and fixing microorganisms in a treatment tank and a method for wastewater treatment using the same have been known so far.
However, the method and the apparatus using existent fixed carriers involve problems, for example, that gases generated in the treatment tank are deposited to the carriers thereby tending to rise the carrier, it is difficult to suppress occurrence of channeling referred to as water channel in the carrier filled region and further substrate and oxygen do not permeate and diffuse rapidly into the carriers.
While studies have been progressed in view of the shape and the structure of the carrier in order to improve the situations described above, they have not always provided sufficient effect at the present situation. For example, this can be seen also in a case of a microorganism deposition type cord carrier in which microorganisms are deposited and fixed to a string-like support. For the submerged filter bed method using the microorganism deposition type cord carrier, the following problems are pointed out.
That is, at first, it takes a long time for the wastewater treatment operation to reach a stationary state. This is because it takes a long time for microorganism communities that are spontaneously formed in the treatment tank (activated sludge, anaerobic sludge) and effective to wastewater treatment to deposit on the surface of the cords and grow to a sufficient amount required for the treatment.
Secondly, when solids are contained in the wastewater, the treatment efficiency is remarkably lowered. This is because the microorganism communities deposited and grown on the cord are exposed directly to wastewater and, accordingly, the microorganism communities are formed upon inflow or stirring of wastewater by kinetic energy of solids. Under such a circumstance, the concentration of outflowing solids increases more in the treated water than that before treatment to worsen the water quality.
Thirdly, it requires considerable experience and knowledge for maintenance. When microorganism deposition type cords are utilized, sludges are sometimes deposited excessively on the cords to cause channeling in the treatment tank. For preventing this, excess sludges have to be removed by backwashing relying on operators"" knowledge and intuition. This also requires back washing pipelines and facilities which lead to an increased cost.
Fourthly, it is sensitive to bulking. Particularly, when filamentous bacteria appear in the aerobic wastewater treatment, they become dominant species to expel other useful microorganisms, which is referred to as bulking to reduce the treatment efficiency. Since the useful microorganisms on the deposition type cords are exposed directly to wastewater, they directly undergo the effects of the filamentous bacteria and die. If such a state should occur, it is necessary to take out the deposition type cords entirely from the treatment tank and completely wash them.
Since the problems as described above are substantially in common with carriers of other shapes and structures, it has been demanded for a drastical improvement capable of dissolving the existent problems as described above such as floating of the carrier by the generated gases, occurrence of channeling and slow penetration and diffusion of the substrate and oxygen into the carrier, and the problem as in the case of the cord carrier.
For solving the foregoing subjects the invention of the present application provides at first a magnetic sludge characterized by containing microorganisms and having reactivity to magnetic field.
Further, the invention of the present application provides, secondly, a magnetic sludge in which paramagnetic material is contained and, thirdly, a magnetic sludge using a polymer as a support and, fourthly, a magnetic sludge in which the polymer comprises an insolubilized chitosan or polyvinyl alcohol.
Then, the invention of the present application provides, fifthly, a method for preparing a magnetic sludge containing microorganisms and having magnetic field reactivity in which paramagnetic material and a concentrated sludge are caught and supported on a polymer as a support and, sixthly, a preparation method in which a polymer comprises an insolubilized chitosan or polyvinyl alcohol.
Further, the invention of the present application, provides, seventhly, a method for wastewater treatment using the magnetic sludge according to any one of the first to fourth inventions in which the movement of the magnetic sludge is controlled by a magnetic force, eighthly, a method for wastewater treatment in which denitrification and methane fermentation are conducted simultaneously in one tank and, ninthly, a method for wastewater treatment for retaining the magnetic sludge to porous concretes.
Further, the invention of the present application provides, tenthly, a method for wastewater treatment by a treatment tank in which an inclusive fixed carrier possessing microorganisms and having magnetic property is filled in a submerged fixed filter bed in which the wastewater treatment is conducted by controlling the position of the magnetic inclusive fixed carrier in water by the change of the direction of the magnetic field by an external magnetic field.
Regarding the method described above, the invention of the present application provides, eleventhly, a method for wastewater treatment in which the inclusive fixed carrier is constituted as a beads-like, plate-like, cord-like or agglomerated sludge-like form.
Twelfthly, it provides a method for wastewater treatment in which the magnetic control is conducted by a permanent magnet or a solenoid coil.
Then, the invention of the present application provides, thirteenthly, a method for wastewater treatment of incorporating an inclusive fixed carrier possessing microorganisms and having magnetic property in a submerged fixed filter bed, in which a magnetic force application device is disposed for controlling the position of the inclusive fixed carrier in water by the change of the direction of the magnetic field and, fourteenthly, an apparatus for wastewater treatment in which the inclusive fixed carrier is constituted as a beads-like, plate-like, cord-like or agglomerated sludge-like form, fifteenthly, an apparatus for wastewater treatment in which the magnetic force application means comprises a permanent magnet or solenoid coil and, sixteenthly, an apparatus for wastewater treatment in which the magnetic force application device provides a fixed or variable magnetic field.